/*
 * Copyright 2015 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.netty.handler.codec;

import static io.netty.util.internal.ObjectUtil.checkNotNull;

/**
 * Result of detecting a protocol.
 *
 * @param <T> the type of the protocol
 */
public final class ProtocolDetectionResult<T>
{

    @SuppressWarnings(
    { "rawtypes", "unchecked" })
    private static final ProtocolDetectionResult NEEDS_MORE_DATE = new ProtocolDetectionResult(
            ProtocolDetectionState.NEEDS_MORE_DATA, null);

    @SuppressWarnings(
    { "rawtypes", "unchecked" })
    private static final ProtocolDetectionResult INVALID = new ProtocolDetectionResult(
            ProtocolDetectionState.INVALID, null);

    private final ProtocolDetectionState state;

    private final T result;

    /**
     * Returns a {@link ProtocolDetectionResult} that signals that more data is
     * needed to detect the protocol.
     */
    @SuppressWarnings("unchecked")
    public static <T> ProtocolDetectionResult<T> needsMoreData()
    {
        return NEEDS_MORE_DATE;
    }

    /**
     * Returns a {@link ProtocolDetectionResult} that signals the data was
     * invalid for the protocol.
     */
    @SuppressWarnings("unchecked")
    public static <T> ProtocolDetectionResult<T> invalid()
    {
        return INVALID;
    }

    /**
     * Returns a {@link ProtocolDetectionResult} which holds the detected
     * protocol.
     */
    @SuppressWarnings("unchecked")
    public static <T> ProtocolDetectionResult<T> detected(T protocol)
    {
        return new ProtocolDetectionResult<T>(ProtocolDetectionState.DETECTED,
                checkNotNull(protocol, "protocol"));
    }

    private ProtocolDetectionResult(ProtocolDetectionState state, T result)
    {
        this.state = state;
        this.result = result;
    }

    /**
     * Return the {@link ProtocolDetectionState}. If the state is
     * {@link ProtocolDetectionState#DETECTED} you can retrieve the protocol via
     * {@link #detectedProtocol()}.
     */
    public ProtocolDetectionState state()
    {
        return state;
    }

    /**
     * Returns the protocol if {@link #state()} returns
     * {@link ProtocolDetectionState#DETECTED}, otherwise {@code null}.
     */
    public T detectedProtocol()
    {
        return result;
    }
}
